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Title:
APPARATUS AND METHOD FOR PRODUCTION OF GRAPHENE PRODUCTS
Document Type and Number:
WIPO Patent Application WO/2018/031455
Kind Code:
A1
Abstract:
A method for producing graphene includes feeding a carbon source into a reaction chamber, passing a catalytic substrate disposed on a surface of a cylindrical body through the reaction chamber by rotating the cylindrical body around its axis, heating the substrate in the reaction chamber to produce graphene on the substrate from the carbon source, and releasing the graphene from the substrate outside the chamber. An apparatus for producing graphene includes a reaction chamber holding a carbon source, a heat source, a cylindrical body, and a catalytic substrate disposed on the cylindrical body. The cylindrical body rotates and passes the substrate through the reaction chamber. The reaction chamber encloses a pari of the cylindrical body to expose the substrate on that part of the body to the carbon source, and the heat source heats the substrate in the chamber to yield graphene deposits on the substrate.

Inventors:
SHELLEY WILLIAM FRANKLIN (US)
OFLYNN DONAL PAUL (IE)
MOYNAGH PHILLIP BERNARD (IE)
Application Number:
PCT/US2017/045709
Publication Date:
February 15, 2018
Filing Date:
August 07, 2017
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
SHELLEY WILLIAM FRANKLIN (US)
OFLYNN DONAL PAUL (IE)
MOYNAGH PHILLIP BERNARD (IE)
GRAPHENEXL LTD (IE)
International Classes:
C01B32/205; B01J8/08; B01J8/10
Foreign References:
US20120025413A12012-02-02
CN103435035A2013-12-11
CN103103493A2013-05-15
US20120128573A12012-05-24
KR20120010643A2012-02-06
EP3173379A12017-05-31
Attorney, Agent or Firm:
BERMAN, Jane, S. (US)
Download PDF:
Claims:
CLAIMS:

1. A method for producing graphene, comprising:

feeding a carbon source into a reaction chamber:

passing a catalytic substrate disposed on a surface of a cylindrical body through the reaction chamber by rotating the cylindrical body around a central axis of the cylindrical body;

heating the substrate in the reaction chamber to a graphene production temperature to produce graphene on the substrate from the carbon source; and

releasing the graphene from the substrate outside the reaction chamber.

2. The method according to claim 1 , further comprising cooling the substrate outside the reaction chamber,

3. An apparatus for producing graphene, comprising:

a reaction chamber configured to hold a carbon source;

a heat source;

a cylindrical body; and

a catalytic substrate disposed on a surface of the cylindrical body, wherein the cylindrical body is configured to pass the substrate through the reaction chamber as the cylindrical body rotates around a central axis of the cylindrical body,

the reaction chamber is configured to enclose a portion of the cylindrical body within the reaction chamber to expose the substrate on that portion to the carbon source, and

the heat source is disposed to heat the substrate in the reaction chamber.

4. The apparatus according to claim 3, wherein the heat source is disposed inside the cylindrical body.

5. The apparatus according to claim 3, wherein the heat source is disposed outside the cylindrical body.

6. The apparatus according to claim 3, further comprising a cooling apparatus disposed to cool the substrate on a side of the cylindrical body that is rotated outside the reaction chamber,

7. The apparatus according to claim 3, wherein the cylindrical body is a drum.

8. The apparatus according to claim 3, further comprising a stationary core, wherein the cylindrical body is a hollow cylinder that rotates around the stationary core.

9. The apparatus according to claim 8, wherein the heat source is disposed inside the stationary core.

10. The apparatus according to claim 9, further comprising a cooling apparatus disposed inside the stationary' core and configured to cool the substrate on a side of the cylindrical body that is rotated outside the reaction chamber.

11. The apparatus according to claim 3, further comprising a laser disposed outside the reaction chamber and configured to remove the graphene from the substrate.

12. The apparatus according to claim 3, wherein the substrate is a wire winding around the surface of the cylindrical body.

13. The apparatus according to claim 3, wherein the substrate is a foil applied to the surface of the cylindrical body.

14. The apparatus according to claim 7, wherein cylindrical body comprises an inner metallic core and an outer ceramic layer on which the substrate is disposed.

15. The apparatus according to claim 3, wherein the cylindrical body rotates around an axle disposed along the central axis of the cylindrical body and supported by a bearing of the apparatus.

Description:
DESCRIPTION

TITLE OF INVENTION : APPARATUS AND METHOD FOR PRODUCTION OF GRAPHE E PRODUCTS

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the priority of U.S. Provisional Patent Application No. 62/372,246 filed August 8, 2016; U. S. Provisional Patent Application No. 62/401,041 filed September 28, 2016; U. S. Provisional Patent Application No. 62/401,056 filed September 28, 2016; and U.S. Provisional Patent Application No. 62/474,238 filed March 21 , 2017, and the contents of all of these applications are incorporated by reference herein in their entirety. TECHNICAL FIELD

[0002] The technical field relates to apparatus and methods for producing graphene-based carbon fibers and large area graphene sheets. More particularly, the technical field relates to an apparatus and method for continuous production of such fibers and sheets employing a rotating drum structure having a substrate on its outer surface for formation of graphene in a decatenation process.

BACKGROUND

[0003] There remains a continuing need for improved apparatus and methods for producing high modulus, high tensile strength graphene-based carbon fibers and large area graphene sheets, in some current methods, high performance carbon fibers are primarily made from a polyaerylomtrile (PAN) precursor fiber that is oxidized and then carbonized. Fifty percent of the cost of the end product carbon fiber is attributed to the PAN precursor. Forty percent of the total cost of production of PAN based carbon fibers arises from the energy intensive high temperature oxidation and carbonization processes. The final ten percent of the cost is attributed to post-treatment of the carbon fibers. Research into carbon fibers produced from other precursors such as pitch, polyolefms, and iignins have failed to produce carbon fibers with the requisite tensile strength and elastic modulus.

[0004] Presently, production of large area graphene sheets has been limited to laboratory- scale research and development. The graphene sheets themselves are limited in length and width to a few inches in each dimension. The sheets are typically made in a chemical vapor deposition (CVD) system in batch mode. High cost factors, complicated equipment configurations, and lack of high volume, continuous-mode production of graphene, particularly in large area format, have limited production to an extent that has impaired incorporation of graphene into a broad range of useful applications and products. [0005] Thus, improvements are needed in methods and apparatus for cost-effective production of graphene products.

SUMMARY

[0006] Embodiments of the invention relate to an apparatus and method for producing graphene-based carbon fibers and large area graphene sheets. The apparatus and method employ a catalyst substrate provided on the surface of a cylindrical rotating drum-type structure that rotates the substrate surface into and out of a reaction chamber, in the nature of a reactor vessel, where a carbon precursor in the nature of a hydrocarbon source is exposed to the catalyst substrate at a high temperature. The apparatus and method cause thermal decatenation of the hydrocarbon and cause the resulting carbon to deposit on the substrate in the form of graphene. Various embodiments of the surface of the drum holding the catalyst offer varied output formats of graphene in yarn and sheet formats. Embodiments of the apparatus and method include heating and cooling equipment and steps to aid the production process. The apparatus and method further comprise structures and steps for efficient removal of the graphene from the substrate in yarn and sheet form.

[0007] While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is a schematic diagram of an apparatus according to some embodiments of the invention.

[0009] FIG. 2 is a perspective view of a schematic representation of a drum with a continuous substrate wire winding, according to some embodiments.

[0010] FIG. 3 is a perspective view of a schematic representation of a drum with substrate loops, according to some embodiments.

[0011] FIG. 4 is a perspective view of a schematic representation of a drum with substrate foil or substrate coating, according to some embodiments.

[0012] FIG. 5 is a schematic partial cross-sectional view of a drum with ridges, according to some embodiments.

[0013] FIG. 6 is a perspective view of a schematic representation of a drum with fins, according to some embodiments.

[0014] FIG. 7 is a perspective view of a schematic representation of a drum structure comprised of a pluralit ' of drum sections, according to some embodiments. [0015] FIG. 8 is a schematic diagram of a drum with a ceramic layer, according to some embodiments.

[00Ϊ6] FIG. 9 is a schematic diagram of a drum with an internal heat source, according to some embodiments.

[0017] FIG. 10 is a schematic diagram of a drum with a ceramic layer and an internal heat source, according to some embodiments.

[0018] FIG. 11 is a schematic diagram of an apparatus including a drum with a ceramic layer and an internal heat source, according to some embodiments,

[0019] FIG. 12 is a schematic diagram of an apparatus including a rotating tube and stationary core, according to some embodiments.

[0020] FIG. 13 is another schematic diagram of an apparatus including a rotating tube and stationary core, according to some embodiments.

[0021] FIG. 14 is a schematic diagram of a heat exchanger of the stationary core, according to some embodiments.

[0022] FIG. 15 is a schematic diagram of an apparatus including a cooling gas system, according to some embodiments,

[0023] FIG. 16 is a perspective view of a schematic representation of an apparatus according to an embodiment of the invention.

[0024] While the invention is amenable to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are described in detail below. The intention, however, is not to limit the invention to the particular embodiments described. On the contrary, the invention is intended to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

[0025] In an embodiment, an apparatus is provided for production of graphene using a carbon source, preferably in the nature of a hydrocarbon source, as a precursor. The apparatus 2, schematically depicted in the diagram of FIG. 1, includes a reaction chamber 4 for containing the hydrocarbon source HC in a gaseous form, and a rotating cylindrical body, here shown in the nature of a drum 6, that is configured and disposed such that, during rotation of the drum, its outer surface travels through the reaction chamber 4, exposing the outer surface to the hydrocarbon source HC contained in the reaction chamber 4. The surface of the drum 6 is coated with or carries a substrate 8 that is or contains a catalyst for decatenation of hydrocarbon gases at high temperatures, and thus the substrate 8 serves as a graphene growth catalyst. While the outer surface of the drum passes through the reaction chamber 4 during rotation of the drum 6 on its axle 10, the substrate 8 is exposed to high temperatures, triggering a catalytic decatenation reaction, whereby carbon is released from the hydrocarbon source HC, and deposits as graphene fibers on the substrate 8.

[0026] As the drum 6 continues to rotate, the substrate 8 bearing the deposited graphene travels out of the reaction chamber 4, where exposure to lower temperatures and removal apparatus (such as laser 12) are employed to remove the deposited graphene coating from the substrate 8, and the graphene product is harvested in string, yarn, or sheet form. The graphene product is schematically represented by reference numeral 14 in the figures. In FIG. 1, the graphene product 14 is represented in a string form.

[0027] In an embodiment, the hydrocarbon precursor is fed into the reaction chamber. The hydrocarbon precursor may be a gaseous precursor such as methane or ethylene. The precursor may be a solid or liquid precursor such as petroleum j elly, paraffin wax, or similar hydrocarbon precursor that may boil and become gaseous at the reactor temperature. Liquid precursor hydrocarbons sources may be introduced into the reactor chamber 4 via a liquid- holding reservoir 16 to fill the reactor chamber with gaseous vapors upon increase in temperature. A liquid precursor may be applied directly to the substrate 8 via a dip coating or spraying method. The apparatus and method preferably are adapted for use of different precursors, and preferably are adapted for use of multiple precursor sources at a given time, to maximize flexibility in precursor sourcing and cost profile.

[0028] A representative example of the thermal decatenation reaction using a methane precursor in the presence of a catalyst is:

CH 4 + heat→ C + 2H 2

[0029] In this example, the carbon is dissociated from the hydrogen at a processing temperature which may be in a range of approximately 700 degrees C to approximately 1400 degrees C, depending on the carbon source used, the catalyst used, and other processing conditions in the reaction chamber. The carbon deposits on the catalyst substrate in the form of graphene. Upon the thermal dissociation of the hydrocarbon, hydrogen gas is also produced. The liberated hydrogen gas may then be separated from the hydrocarbon gases at an outlet 18 of the reaction chamber 8 and used for other purposes.

[0030] In the apparatus 2, the surface of the rotating, cylindrically-shaped drum 6 is coated with or carries a substrate 8 formed of or containing a catalyst for thermal decatenation of hydrocarbon gases, and which thus is a graphene growth catalyst. The rotation of the cylindrical drum 8 around its central longitudinal axis (axis A, see FIG. 2) passes the substrate 8 into and back out of the reaction chamber 4 for the production of graphene based carbon fiber and large area graphene sheets 14.

[0031] Any graphene growth catalyst material may be used as the substrate 8. Preferably, the substrate material is comprised principally of copper, nickel, iron, rhenium, ruthenium, platinum, stainless steel, nickel-based alloys, which may include a nickel-based alloy such as the one sold under the trademark ALUMEL (TM, Concept Alloys, Inc.), nickel/chromium alloys, which may include a nickel/chromium-based alloy such as the one sold under the trademark CHROMEL (TM, Concept Alloys, Inc.), iron with chromium coating, iron with rhenium coating, SiC coated with any of the metals listed above, or AI2O 3 coated with any of the metals above, etc. The inventors have discovered that more preferably for application in the embodiments herein the substrate material is comprised principally of nickel.

[0032] The substrate 8 may be a discrete material held in place on the surface of the drum 6, or may be a coating applied directly to the drum surface. In an embodiment, a thermal barrier coating may be interposed between the drum 6 and the substrate 8. For example, a yttria- stabilized zirconia coating may be affixed to a steel body of the drum 6, and then the substrate formed or affixed to the yttria-stabilized zirconia coating, such that the zirconia coating forms a thermal barrier between the substrate 8 and the body of the drum 6. Discrete substrate material may be provided in the form of a very thin foil of the substrate material applied to the surface of the drum, or as a wire or ribbon formed of substrate material and wound around the circumference of the drum. The wire may preferably be in the form of a wire having a circular or ovoid shape in cross-section. The wire may preferably be in the form of a flat ribbon wound around the drum. Some schematic representations of substrate 8 configurations are shown in FIG. 2 (continuous wire winding); FIG. 3 (separate wire loops); and FIG. 4 (foil or coating). A wire form of the substrate may preferably have a circular shape in cross-section with a chord diameter of approximately ten micrometers to approximately ten millimeters. The substrate wires or foils are fitted tightly onto the circumference of the drum, as schematically shown in FIGS. 2-4. Tens to millions of substrate wires may be fitted onto a single drum.

[0033] The materials forming the bod}' of the drum 6 may be chosen such that the coefficient of thermal expansion (CTE) of the drum 6 slightly exceeds the thermal expansion of the substrate 8, whether in wire, foil, or coating form. In this way, as the drum 6 is heated to the process temperatures, the substrate wire or ribbon windings, or foil, will be disposed in slight tension around the circumference of the outer surface of the drum, rather than loosely fitting around the drum.

[0034] The substrate 8 wire or foil, supported by the outer circumference of the drum, may be used in the production process many times before needing replacement. Such reuse presents advantages over prior processes that do not allow such reuse, for example, those that involve dissolving the substrate in order to remove the graphene from the substrate. Stretching, creep, and breakage of the substrate wire, ribbon, or foil are the most typical circumstances requiring replacement of the substrate.

[0035] As contrasted with prior art systems lacking a drum supporting the substrate, in embodiments of the invention, the outer surface of the drum provides uniform support to the substrate wires/foils, providing physical support from the inner side of the wound wires or foils and more evenly distributing stresses along the length of the substrate wires or foils, thus increasing the lifetime of the substrate wires and foils, and accordingly, reducing the operating expense associated with production of graphene using the apparatus and method.

[0036] As schematically depicted in FIG. 2, a continuous length of substrate wire may be wound around the drum 6, as a fabric sewing thread is wound on a bobbin or spool. In this manner, the left end of substrate wire and the right end of substrate wire would be pulled in tension to ensure a tight fit around the drum. The successive windings of a continuous length of substrate wire around the drum may essentially be parallel to one another, due to the fact that the wire diameter is very small, micrometers to millimeters, as contrasted to a large diameter of the drum, up to several meters in circumference.

[0037] An advantage of using the configuration of FIG. 2 of a continuous length of substrate wire wound around the drum is that this allows the substrate wire to be rewound and reused repeatedly, instead of being consumed in the process as in prior art methods. The reuse opportunity may dramatically reduce operating expenses associated with this apparatus and method.

[0038] In an embodiment, the substrate 8 in a wire or ribbon form may be formed into a seamless loop as schematically shown in FIG. 3. This may be accomplished by cutting wires into segments of an appropriate length to be fitted around the circumference of the outer surface of the cylindrical drum 6, such that a circumference of an inner surface of the loop is matched to a circumference of the outer surface of the drum 6. The circumference of the inner surface of the loop may be selected to provide for a tight fit around the circumference of the drum, after correcting for the effect of differing coefficients of thermal expansion of the drum material and the substrate material. The two ends of each cut wire piece are attached to one another using laser welding, brazing, soldering, or a mechanical coupler to form the loop. The finished wire loop may be about one meter to many meters in circumference, depending on the size of the circumference of the outer surface of the drum.

[0039] In an embodiment, the substrate 8 may be in a continuous layer form, applied as a foil affixed to the outer surface of the drum 6, or as a coating applied to the surface, as schematically depicted in FIG. 4. The width of outer surface of the drum measured along the direction of the longitudinal axis A of the drum may establish the maximum width of the substrate in its foil or coating form. The thickness of the foil may preferably be minimized to minimize the cost of the substrate, but the foil should be thick enough to maintain mechanical integrity.

[0040] In an embodiment, the substrate material may be coated directly onto the outer circumference of the drum 6. In an embodiment, the outer surface of the drum 6 is a smooth flat surface around the circumference of the drum onto which the substrate material is coated to form the layer of substrate 8. The coating may be accomplished by physical vapor deposition techniques such as sputtering or thermal evaporation, by electrochemical techniques such as electrolytic deposition, and/or by electroless chemical techniques. The thickness of the deposited substrate material layer may be selected to provide the appropriate diffusion depth for the desired number of graphene layers to be deposited on the substrate layer. The coefficient of thermal expansion may also be tailored for optimal graphene release from the substrate by the use of the core substrate coated with a thin film of substrate material. Iron and rhenium are examples of catalyst substrate materials that may be applied by a coating process.

[0041] An advantage of a coating process being used to apply the substrate 8 to the drum 6, and of the resulting drum structure, is that a large area, flat sheet of graphene may be deposited onto the surface of the substrate layer on the drum.

[0042] An embodiment is schematically depicted in a cross-sectional view of a drum 6 of FIG. 5, taken along a line of a plane of a diameter of the drum 6. As depicted in FIG. 5, instead of a flat smooth outer circumferential surface of the drum 6, ridges 20, 20 extend radially outwardly from a central portion of the drum 6, and surround the central portion of the circumferential outer surface of the drum 6. The ridges 20, 20 are machined or formed into the outer surface of the drum 6 to form a ridged outer surface of the drum 6. Then, the ridged surface is coated with the substrate material to form the substrate 8 in a layer applied to the ridges 20, 20. In this way, the total surface area of the catalytic substrate layer may be increased, relative to the size of the diameter and of the width of the drum 6. This ridged outer surface configuration having a higher total outer surface area helps to maximize graphene throughput for a drum having a given diameter size.

[0043] In an embodiment as schematically depicted in FIG. 6, the drum 6 may comprise fin- like structures wherein protrusions extend outwardly radially from an outer circumferential surface of the central portion 24 of the drum. The drum 6 may be formed with the fins 22, 22 or may have the fin structures machined into the drum. Each fin 22 may have a shape that is essentially rectangular in cross-section, with a flat outermost (top) surface. The circumference of the circle defined by the outermost portion (top surface, at the point of reference numerals 22, 22 in FIG. 6) of each of the fins is larger than the circumference of the circle defined by the outermost portion of the central portion 24 of the drum. All vertical and horizontal surfaces of the drum equipped with the fins 22, 22 are then coated with substrate material as described above, so that a substrate 8 is formed on the central drum surfaces as well as the fin surfaces. The graphene may then be formed by the decatenation process on any of the horizontal or vertical surfaces of the drum 6 having the fins 22, 22. In this way, the total width of the substrate surface may be increased relative to the width of the drum 6, measured in the direction along the longitudinal axis A of the drum. This may increase the maximum width of a graphene sheet that may be produced on a drum 6 having a given width in the direction of its longitudinal axis A. This may also maximize throughput of graphene production relative to a given width of the drum or apparatus.

[0044] In an embodiment, the drum 6 is driven rotationally by a drive motor system of the apparatus, schematically depicted at reference numeral 26 in FIG. 1. The drive motor system 26 may be operatively engaged by a gear system or other known forms of mechanical engagement to rotate an axle 10 of the drum 6, causing rotation of the drum 6, via action of an electric drive motor of the system 26. The axle may be supported by a bearing structure that forms a part of the apparatus and supports the axle, so as to support the cylindrical body as it rotates on the axle to pass the substrate through the reaction chamber. The electric motor may have electrical power supply connectors and electronic communications connectors for power supply and electronic control of drive operations, such as rotation speed, by a computer or other electronic controller component. The axle 10 may be disposed along the central longitudinal axis A of the drum, in the center of a central hollow drum space which may include spoke-like linkages connecting the axle 10 to the body of the drum 6.

[0045] In an embodiment of the apparatus, the rotating drum 6 may be driven by an edge-on gear drive mechanism of the drive motor system 26, schematically represented in FIG. 16. The gear drive mechanism may be positioned to operatively engage at least one of the longitudinal ends of the drum 6 with the electric drive motor via a gear system or other known forms of mechanical engagement that engage the drum end with the motor to drive rotation of the drum 6 by action of the motor.

[0046] Features of the rotating drum may be selected or adjusted to affect the type and characteristics of the graphene produced. The drum may be rotated at sufficient speeds in the reaction chamber such that graphene may be deposited at a rate that may be as high as the speed of sound, and very high output of graphene per unit of time can be achieved. The rotational speed (e.g., rotations per minute, RPM) of the drum may be selected to provide an optimal residence time in the reaction chamber for production of the particular form and/or depth of graphene deposits desired. For example, a range of one to 500 RPM may be selected as a rotational speed at which a drum 6 of a given diameter turns in order to achieve a desired residence time in the reaction chamber. In an embodiment, a residence time of a given radial segment of the substrate 8 borne on the rotating drum 6 may be selected to be within a range of less than one second to about ten seconds. A target residence time in the reaction chamber may be selected to be the minimum time at which a graphene product having one to ten layers is produced. A preferred target number of graphene layers to be produced in a cycle within the reaction chamber may be set at three to seven layers. A preferred target production rate may be set to be production of a five layer sheet of graphene within a residence time of less than one second.

[0047] The diameter of the rotating drum may be selected to provide an optimal residence time in the reaction chamber of the substrate layer positioned on the circumference of the drum in order to achieve production of the particular form or depth of graphene deposits desired. At a constant rotational speed (RPM), a drum having a larger radius provides a higher linear velocity (and accordingly a lower residence time in the chamber) of the substrate layer than a drum having a smaller radius. Thus by varying rotation speed, or by selecting drums of different diameters for installation in the apparatus, conditions may be varied in the apparatus and method in order to favor production of particular types of graphene structures.

[0048] The drum may be formed in the shape of a solid cylinder having a central axle, as described above. The solid drum is depicted in FIG. 2.

[0049] In an embodiment, the rotating drum may preferably be comprised of a plurality of cylindrically-shaped drum sections. The drum sections may be in an arrangement next to one another, preferably abutting, along their longitudinal axes, to form a wide version of the drum as schematically depicted in FIG. 7. An advantage of this arrangement is flexibility and ease in maintenance, replacement, and repair, in that one section of the drum having a defect or excessive wear may be replaced without necessity of replacing the entirety of the drum. The replacement drum section may be prepared offline during a production cycle, and then quickly exchanged for the defective section, with minimal disruption to the continuous graphene production process. A drum 6 formed using such abutting drum sections may be assembled in a manner that the overall longitudinal length of the drum may be tens or hundreds of meters, but the individual drum sections may be on the order of meters. This drum section construction also allows flexibility in the overall total width of the graphene sheet produced, via selection of how many of the drum sections to employ for a given production run.

[0050] In an embodiment, the rotating drum may be comprised of one material, such as a metal, a metal alloy, or a refractory ceramic material, schematically depicted in FIG. 2. The drum may be comprised of a ceramic/metal composite, which combines the high thermal conductivity and mechanical toughness of the metal, with the refractory and strength of a ceramic material. The material of which the drum is comprised may preferably be a material or a combination of materials that can withstand temperatures up to 1500°C.

[0051] In an embodiment, the rotating drum may have a layered construction, with layers having different material compositions provided at different positions along a radius of the drum. An example is schematically depicted in the side view diagram of FIG. 8, wherein the layered construction may comprise a drum core 28, which may be formed of a metallic material, surrounded by a ceramic outer layer 30 positioned on the outer periphery of the drum core 28. The ceramic layer in turn has positioned on its outer periphery the substrate 8. The ceramic layer will provide an adiabatic environment, to maintain constant, high temperatures at the substrate 8. The composition of the material of which the ceramic layer 30 is comprised may be selected to have a coefficient of thermal expansion and other physical and mechanical properties desirable for formation of particular forms and/or depth of graphene deposited, and/or for ease of release of the produced graphene structures from the substrate 8 after exit from the reaction chamber 4.

[0052] The ceramic layer 30 may be a solid, continuous ceramic layer around the outer circumference of the drum core 28. In an embodiment, the ceramic layer is a segmented ceramic layer as schematically depicted in FIG. 8. In the structure of a drum having a segmented ceramic layer, segments 32, 32 formed of ceramic materials may be disposed around the circumference of the drum core 28, with gaps 34, 34 between the segments filled in with a material different than the ceramic material, for example, a material the same as a metallic material of the drum core 28. This segmented layer construction may allow for better performance under heat stress, due to the fact that most ceramic materials have coefficients of thermal expansion (CTEs) that are much lower than those of metallic materials. Thus a continuous ceramic outer layer may be more prone to cracking due to a CTE mismatch between layers during exposure to large changes in temperature, and the gaps may moderate the differential in CTEs.

[0053] In an embodiment of the apparatus, it is contemplated that heat to drive the thermal decatenation of the hydrocarbon source may be supplied by a heat source in the reaction chamber that is external to the drum. For the case of a non-heated drum (schematically depicted in FIGS. 2 and 8), the drum may be assembled into a reaction chamber 4 that includes an external heat source as described in more detail below.

[0054] In another embodiment, a heat source inside the rotating drum 6 is provided. This internal heat source within the interior of the rotating drum 6 may be provided in addition to or in place of an external heat source, described in more detail below. Configurations for examples of internally-heated rotating drums 6 are shown in the schematic side views of FIGS. 9 and 10. FIG. 9 shows an example of an internal heat source 36 inside the body of a rotating drum 6, and FIG. 10 shows another example wherein an internally -heated rotating drum includes an internal heat source 36, as well as a segmented outer ceramic layer 30 similar to that of the embodiment shown in FIG. 8. Internally -heated rotating drum structures may comprise an internal heating apparatus 36, such as one or more of resistive heating elements, microwave heating elements, combustion burners, or induction coils. The hydrocarbon feedstock HC is fed over the drum 6 in a thin film within the reaction chamber 4. A thin-film feed of the hydrocarbon feedstock over the substrate 8 on an internally-heated drum provides the maximum hydrocarbon/substrate interaction volume per unit of surface area of substrate, and will therefore provide more efficient use of the hydrocarbon feedstock HC as well as efficient use of the energy consumed in providing the heat.

[0055] Heating the drum internally provides conductive heat transfer from the drum 6 to the substrate 8that improves the thermal efficiency of the overall system as compared to an externally-heated configuration. In the case of an external heat configuration, the reaction chamber 4 is heated and convective heat transfer to the substrate 8 is required, through the gases in the reaction chamber 4, which is less efficient than conductive heat transfer. Thus for the case of an internally-heated drum structure as schematically shown in a side view diagram of FIG. 11, the thermal efficiency should be significantly higher than in the case of an externally heated system. The higher efficiency is due to conductive transfer of heat emitted from the internal heat source 36 through the drum core 28 and the ceramic layer segments 32, 32 to reach the substrate 8, as schematically depicted in FIG. 11. Also, by using an internally-heated drum, the complexity of the overall apparatus may be reduced, lowering the cost of assembling, maintaining, and operating the apparatus 2.

[0056] In another embodiment, the apparatus comprises a rotating cylindrical body having another configuration as contrasted to the rotating drum structures shown in FIGS. 1 -4 and 8- 10. In this embodiment, the rotating cylindrical body may be in the form of a hollow cylinder or tube 38 as schematically shown in a side view diagram in FIG. 12. The rotating hollow tube 38 carries on its outer surface the substrate 8. The substrate layer has a similar operation as described above with respect to the substrate layer on the drum, and may be applied to the outer surface of the rotating hollow tube by means and methods similar to those described above with respect to the solid drum structure, such as application by wire or ribbon loops or windings, foils, or coatings.

[0057] The hollow tube 38 is at least partially disposed inside the reaction chamber 4 so as to expose the substrate 8 to the hydrocarbon HC stream contained in the reaction chamber 4. The hollow tube 38 rotates around a stationary core 40 as schematically shown in FIG. 12, so as to move the substrate 8 through the reaction chamber 4, in a similar manner as the solid drum construction described above moves the substrate 8 through the reaction chamber 4. The rotation of the hollow tube 38 around the stationary core 40 may be driven by a motor that is operationally engaged to drive one or more edge-on gear drive mechanisms positioned at one or both of the longitudinal ends of the rotating tube 30 (in a manner analogous to the drive system 26 depicted in FIG. 1, and described above).

[0058] The rotating hollow tube 38 is comprised of a material that has high thermal conductivity so that heat may be rapidly absorbed by or rapidly removed from rotating hollow tube 38. The material and construction of the rotating tube 38 must be able to withstand high temperatures (up to 1500 degrees C) as well as rapid thermal cycling between hot and cold temperatures. In addition, the rotating tube 38 should have a small thermal mass (e.g., by being relatively thin in its cross-sectional thickness dimension) so that the rotating tube 38 is adapted to heat and cool rapidly. The overall mass of the rotating tube 38 preferably may also be small in order to limit the centrifugal forces acting on the tube 38 as it rotates at high speeds, to control wear on the tube structure and the drive motor system 26.

[0059] Disposed concentrically in an axial direction inside the rotating tube 38 is the stationary core 40 of this embodiment of the apparatus 2, generally formed in the shape of a cylinder. A small gap or space 42 is disposed between the inner surface of the rotating hollow tube 38 and the outer surface of the stationary core 40 to allow for free rotation of the hollow tube 38 around the core 40.

[0060] In an embodiment similar to that described above with respect to the rotating solid drum embodiment, the rotating hollow tube/stationary core construction may also be comprised of a plurality of cylindrically-shaped sections of the tube and core, analogous to the solid drum version depicted in FIG. 7. The tube/core sections may be arranged in abutment with one another along their longitudinal axes, to form a wide version of the rotating hollow tube 38, in a similar manner as shown with respect to the rotating drum configuration depicted in FIG. 7. This arrangement provides similar replacement and repair benefits as previously described with respect to the rotating drum arrangement.

[0061] The stationary core 40 may contain structures and/or devices for heating and/or cooling the rotating tube 38, and hence, the substrate 8 disposed on the outer surface of the tube 38. In an embodiment, an internal heating apparatus 44 of the stationary core 40 is disposed within the stationary core 40 to supply radiated heat to the rotating hollow tube 38 through the inner surface of the tube 38, and conducting in an outwardly radial direction in the tube 38 to reach the substrate 8 disposed on the outer surface of the tube 38. The heating apparatus 44 may include one or more of resistive heating elements, combustion burners, microwave heating elements, or induction coils. In the case of inductive heating, which can provide extremely rapid heating, the stationary core 38 may contain an electrically conductive material as a susceptor for induction. Preferably the heating apparatus 44 is adapted to provide heat up to 1500 degrees C to be supplied to the hollow tube 38, and in turn, to the catalyst substrate 8 disposed on the outer peripheral surface of the hollow tube 38. Predetermined temperatures may be optimized between 1000°C and 1500°C based on the carbon solubility of the hydrocarbon precursor material in use, or of the material of the catalyst substrate layer.

[0062] The rotating hollow tube 38 is disposed partially inside the reaction chamber 4 so that a thin section of hydrocarbon HC precursor gas contained in the chamber 4 is supplied proximate to the catalytic substrate 8 that decatenates the hydrocarbon HC. In an embodiment, the heating mechanism 44 is disposed only on one side of the stationary core 40, namely the side that is positioned within the reaction chamber 4 in a reaction zone, where the hydrocarbon source is contained and the reaction takes place. As shown in FIG. 12, the heating mechanism may be disposed within the stationar ' core 40 along all or most of the portion (semicircular in cross-section) of the stationary core's outer surface that is disposed within the reaction chamber 4. In this manner, heat is provided to the hollow tube 38 only on the side of the stationary core 40 that is positioned in the reaction zone within the reaction chamber 4, where decatenation is conducted.

[0063] As schematically depicted in FIG. 12, an embodiment of the apparatus comprises a cooling mechanism 46 (which may be in the form of a device, a mechanism, or configuration) that is contained within the stationary core 40 and is designed to cool a cooling zone of the apparatus 2. The cooling mechanism 46 may be provided in addition to the heating mechanism 44 as described above. The cooling mechanism 46 may be provided on the side of the stationary core 40 that is opposite to the side having the heating mechanism 44, i.e., provided on a cooling zone area that is generally on the opposite side from the reaction zone of the apparatus 2.

[0064] The cooling mechanism 46 rapidly removes heat from the stationary core 40, and accordingly, provides a cooling effect to the catalyst substrate 8 that has rotated out of the reaction chamber 4 on the hollow tube 38 and now is proximate to the cooling side of the stationary core 40. The temperature decrease performs two functions, namely, (1) to precipitate the carbon that dissolved in the substrate catalyst material out onto the substrate surface to form graphene; and (2) to provide a thermal expansion mismatch between the graphene and the substrate 8, which have different CTEs, thus to provide a shifting force to aid the process of freeing the graphene from the substrate 8. Regardless of the design, means, or steps by which it is constituted, the cooling mechanism 46 must be able to quickly remove heat from the stationary core 40, and accordingly, from the hollow tube portion positioned on the cooling zone side of the apparatus. A large temperature drop is required to precipitate the dissolved carbon from the interior of the substrate catalyst material to form graphene on the surface, and to provide the thermal expansion mismatch to aid the loosening of the graphene from the substrate 8. The cooling mechanism 46 may be optimized to cause a decrease to a specific selected temperature, for example, between 750°C and 1000°C, based on the properties of the catalyst substrate.

[0065] The cooling mechanism or process may employ a number of known means or steps for cooling. A cooling apparatus 46 may include refrigeration apparatus, such as refrigerator coils containing a refrigerant fluid cycled in a heat pump system. A cooling step and apparatus may comprise spraying a cryogenic gas into apertures or recesses formed within the body of the stationary core on its cooling side positioned in the cooling zone of the apparatus.

[0066] In an embodiment, the cooling apparatus and cooling steps may comprise use of a heat exchanger system utilizing cold incoming hydrocarbon HC gas that is the feedstock for the decatenation reaction. For example, as shown in a schematic cross-sectional view of the apparatus 2 in FIG. 13, the heat exchanger 48 disposed inside the stationary core 40 on its cooling side provides cooling to the rotating hollow tube 38 portion that has rotated outside of the reaction chamber 4 and into the cooling zone of the apparatus 2.

[0067] The heat exchanger 48 in the example as shown a schematic side view diagram in FIG. 13 is constituted as one or more pipe-shaped apertures or open pipes formed within the body of the stationary core, preferably formed along the outer surface of the stationary core 40. The pipe-shaped apertures may have a circular shape in cross-section, as may be seen in FIG. 13. The heat exchange effect is provided by forcing flow, by delta pressure, of the relatively cold incoming hydrocarbon precursor gas HC through the pipes formed within the body of the stationary core 40. Forcing flow of the hydrocarbon gas through the pipes causes transfer of heat from the stationary core 40 to the hydrocarbon gas. The pre-heated gas will then flow into the reaction chamber 4, as shown in the directional flow arrows of the hydrocarbon gas HC of FIG. 13. Because the hydrocarbon gas HC input into the reaction chamber 4 has been pre-heated by its circulation through the pipes of the heat exchanger 48, the external heating mechanism of the reaction zone, and the internal heating mechanism 44 on the side of the stationary core 40 near the reaction zone, will not need to provide as much heat to reach the process temperature (i.e., the disassociation temperature of the hydrocarbon gas).

[0068] High flow rates of the relatively cool hydrocarbon gas input into the heat exchanger pipes formed within the stationary core 40 will provide sufficient thermal mass to carry heat away from the stationary core 40 on its cooling side near the cooling zone area of the apparatus 2, and hence, to carry heat away from the substrate layer portion that has rotated into the cooling zone of the apparatus 2 outside the reaction chamber 4. This effect is enhanced if the pipes are formed such that the cool input gas is first directed into pipes formed in close proximity to the outer surface of the cooling side of the stationary core. The heat exchanger may be configured as a plurality of round-trip pipes formed in series as schematically shown in the diagram of FIG. 14, wherein the flow arrows designate cold hydrocarbon gas HC flowing into the heat exchanger 48 pipes, and hot hydrocarbon gas HC flowing out of the heat exchanger 48 pipes. Alternatively, the heat exchanger 48 could be configured as one single pipe formed in a serpentine pathway. Alternatively, the pipes could each form a single-pass pathway from a first end of stationary core 40 to a second end of the stationary core 40 (e.g., from the left side of the heat exchanger 48 as shown in FIG. 14 to the right side, corresponding to a first end and second end, respectively, of the stationary core 40).

[0069] Regardless of the shape of the pipe pathways, the flow of the hydrocarbon feedstock gas through the pipes of heat exchanger 48 may be adjusted to maximize the amount of heat removed from the stationary core. A valve system schematically represented by the "V" of FIG. 13 may have valves that may be adjusted to control of the rate of flow of the feedstock gas into an inlet and/or out of an outlet of the heat exchanger 48. Similarly, the diameter of the heat exchanger pipes, and the spacing between adjacent pipes, could be selected to create a gradient from hot to cold along the outer circumferential surface of the stationary core 40. In this way, cooling rates that are optimal for graphene growth on the substrate 8 may be maintained. In addition, a controlled thermal gradient would help minimize or distribute the thermal stresses that would occur on the surface of the stationary core 40 due to rapid cycling between high and low temperatures.

[0070] Next, features and operation of the reaction chamber 4 will be further described. Conditions in the reaction chamber 4 affect the type of graphene products that may be obtained. Conditions that may be controlled in the reaction chamber 4 to affect production may include temperature; pressure; residence time in the chamber; choice of substrate; doping of substrate; choice of hydrocarbon source HC; and presence of other gases in the chamber.

[0071] The feedstock hydrocarbon gas HC is fed into the reaction chamber 4 at a high flow rate. A gas flow system inputs the hydrocarbon gas into the reaction chamber and causes the liberated hydrogen gas to exit the reaction chamber after decatenation. The flo system is schematically represented as outlet 18 and inlet 50 in FIG. 1 1. Hydrogen gas H 2 that is produced by the decatenation may be removed from the reaction chamber through an outlet 18 (see FIGS. 1 and 11). A gas separation membrane disposed in or near the outlet 18 may be employed to separate the hydrogen gas for removal through the outlet 18. In an embodiment, the hydrogen gas removed from the reaction chamber 4 may thereafter be used as a gaseous fuel for combustion, or may be combined with nitrogen to form liquid ammonia or energy dense liquid fuels.

[0072] The reaction chamber 4 preferably is formed such that a volume of the open cavity containing the hydrocarbon gas within the reaction chamber 4 is minimized relative to the total surface area of the catalyst substrate 8 disposed within the chamber 4. This may be accomplished in part by providing a reaction chamber configuration wherein a distance is minimized between the catalyst substrate 8 disposed in the reaction chamber 4 and the inner surface of the wall defining the outer boundary of the reaction chamber 4. Such a configuration aids in forcing a high proportion of the hydrocarbon gas present in the chamber 4 to be in close proximity to the catalyst substrate 8. This configuration will maximize the percentage of feedstock hydrocarbon HC that is decatenated or dissociated into carbon and hydrogen. This configuration will also eliminate the need for heating a large thermal mass of hydrocarbon feedstock, thus improving overall system efficiency. This small-volume chamber configuration is schematically depicted in FIGS. 11 -13.

[0073] The atmosphere within the heated reaction chamber 4 may be controlled by an atmospheric containment system such as differential pumping through multiple zones of the reaction chamber 4, or electrostatic repulsion so that the catalyst substrate 8 can transition from atmospheric pressure to moderately high vacuums or slightly positive pressures.

[0074] As described above, in addition to the configurations having an internal heating source 36 of the rotating drum 6 (see FIGS. 9-10), or having an internal heating source 44 disposed on a side of the stationary core 40 (see FIGS. 12-13), the reaction chamber 4 may also be provided with a heating apparatus, here referred to as external heating in contrast to the internal heating of the drum or core. The external heating source 52 of the reaction chamber 4 may be any energy source that can provide reaction temperatures up to 1500 degrees C, such as resistive heating, combustion burners, or induction heating. RF or DC plasma may also be used to provide a temperature within the plasma high enough to crack the precursor hydrocarbon to cause the decatenation.

[0075] An embodiment of the reaction chamber 4 may include an external heating source 52 in the form of infrared emitters. The size and shape of the infrared emitters may be chosen to provide the most efficient delivery of the heat to the catalyst substrate 8 disposed within the chamber 4, as well as to provide a controlled temperature gradient to optimize the process steps and minimize thermal stresses on the parts of the apparatus 2.

[0076] The power levels of the infrared emitters may be chosen from a wide variety of power levels from milliwatts to kilowatts. The total thermal flux into the reaction chamber 4 is determined by the number, size, shape, and power levels chosen for the infrared emitters. The process times and temperature determine the required total thermal flux. The wavelength of the infrared radiation can be chosen as well to optimize the absorption of the infrared heat by the catalyst substrate. Ceramic infrared emitters may be preferred as such can provide up to 96% efficiency rates in converting electrical power into heat. Infrared radiation spans wavelengths from 700 nm, which is classified as near infrared (NIR), to 1 mm, which is classified as far infrared (FIR). Typical infrared heating lamps operate in the short wavelength infrared range (SWIR) with wavelengths between 1.4 and 3 μιτι. [0077] In an embodiment, tungsten halogen lamps may be used as the internal and/or external heating source 52. Tungsten halogen lamps are used in rapid thermal processing systems in the semiconductor industry. Halogen heat sources typically operate in the 0.9 to 1.1 μιη wavelength range, and are capable of producing higher radiation intensities.

[0078] In an embodiment, an external cooling gas flow may be provided in the cooling zone of the apparatus to aid the removal of the graphene deposits formed on the substrate. The cooling of the substrate lowers the solubility limit of the dissolved carbon in the substrate. As the temperature drops, the carbon diffuses to the substrate surface where it precipitates and forms graphene. Additionally, the inert cooling gas provides a temperature decrease that leads to an interfacial stress between the substrate surface on the rotating drum or tube on the one hand, and the precipitated graphene on top of the substrate on the other hand. This stress arises due to the differences in the coefficients of thermal expansion between the substrate material and graphene. This interfacial stress aids in the removal of the graphene from the substrate surface.

[0079] As shown in a schematic representation in FIG. 15, the external cooling gas (designated with reference numeral CG) may be directed to flow over the cooling side of the rotating drum 6 of FIGS. 1 and 11, or of the rotating hollow tube 38 of FIGS.12-13, to aid in removal of heat from the catalyst substrate 8 as it travels through the cooling zone of the apparatus 2. The cooling gas CG may be input through an inlet and directed to flow within a cooling gas channel in a direction concurrent to the rotation of the drum 6 or tube 38, or countercurrent to the rotation of the drum 6 or tube 38, depending on one or more of the desired temperature decrease and the desired temperature profile along the circumference of the drum/tube. The concurrent and countercurrent flow directions of cooling gas CG are represented by the reversible arrows shown in FIG. 15. The flow of cooling gas may be directed over any arc length of the circumference of the drum 6 or tube 38, depending on one or more of the desired temperature decrease and the desired temperature profile along the circumference of the drum/tube. The incoming temperature of the cooling gas CG may be controlled from cryogenic temperatures up to the several hundred degrees Celsius, and may be based on one or more of the desired temperature decrease and the desired temperature profile along the circumference of the drum/tube. The temperature of the incoming cooling gas may be controlled to avoid thermal shock of the rotating drum 6 or tube 38, which could result in high mechanical stresses.

[0080] The cooling gas may be an inert gas, including helium, neon, argon, krypton, xenon, and radon, or a combination of one or more of these gases. Argon may be used as an inert gas for industrial processes. Nitrogen, while not technically an inert gas, may be used as a process gas that will not react with the substrate or graphene, depending on the conditions (pressure and temperature). In an embodiment, a reactive gas may be used to both provide cooling and to modify the surface chemistry of the graphene. For example, in certain reaction conditions, nitrogen and/or boron may be used as graphene dopants. Nitrogen doping may be conducted by adding ammonia to methane during the synthesis of the graphene. Boron and nitrogen doping of graphene changes the local electronic structure of the graphene and thus changes the electrical properties of the resulting graphene products.

[0081] As depicted an embodiment schematically depicted in cross-section in the diagram of FIG. 15, the cooling gas channel 54 is a single channel. In an embodiment, the cooling gas flow may be delivered through a plurality of separate cooling gas channels. A channel 54 may provide cooling gas flow having selected conditions, such as one or more of the conditions including a selected flow rate or range of flow rates; a selected incoming gas temperature or temperature range; or selected flow path lengths to precisely control the temperature profile of the substrate as it rotates through the cooling zone. The positions and settings of inlets and outlets of the cooling gas channel may be selected to control such conditions of the cooling gas flow. FIG. 16 shows in a schematic diagram a representation of the stationary core 40 configuration of the apparatus having a cooling gas channel 54, with portions shown in a cut-away view to reveal features inside the stationary core such as the internal cooling apparatus and internal heat source. As schematically depicted in FIG. 16, the cooling gas channel 54 conveys the cooling gas CG along a cooling side or cooling portion of the apparatus in a sheet-like flow, cooling that side of the hollow cylinder 38 as it rotates around the stationary core 40. The cooling gas channel 54 may have a cooling gas inlet and a cooling gas outlet formed within one or more support flanges, which may be configured as supports for holding the parts of the apparatus in their respective positions relative to one another, such as holding the reaction chamber 4 in a position to partially surround the rotating body.

[0082] After decatenation, as the rotating drum 6 or rotating hollow tube 38 continues to rotate, it will convey the substrate 8 bearing the deposited graphene into the cooling zone of the apparatus 2. The cooling process loosens the graphene from the substrate 8 as described above. After cooling, the substrate 8 on the drum or tube bearing the graphene will rotate into a removal zone of the apparatus, where steps and mechanisms are used to remove the graphene from the substrate 8. [0083] In the case of a large area graphene sheet product resulting from, for example, the aforementioned substrate foil or coating method and apparatus, the large area graphene sheet may be removed from the substrate and rolled onto a roller for storage. The width of the graphene sheet is determined by the width of the rotating drum 6 or rotating tube 38. The width of the graphene sheet may be wider than the drum 6 width or tube 38 width, in the case of sheets produced using the features of the ridges 20, 20, or fins 22, 22, previously described, as use of these features will increase the effective graphene production surface area of the drum or tube.

[0084] The apparatus may include a low-power laser 12 provided in a removal zone of the apparatus 2, used to scribe the graphene and split the large-area graphene sheet (which may be formed in the shape of a tube) lengthwise, and the graphene may then be peeled off from the substrate. The removal method and apparatus may pull off of the substrate in large, continuous sheets or ribbons as desired. A large area sheet of graphene may be directly twisted into a yarn filament if desired.

[0085] A beam splitter may be used with a single laser 12 so that a plurality of graphene ribbons may be scribed and released from the substrate simultaneously. The laser 12 may be rastered quickly horizontally to cut the graphene all along a longitudinal series of substrates on drum sections, using a single laser 12. In the case of a graphene sheet, the laser 12 may be used to cut the initial graphene sheet from the substrate 8, and then would not need to be used throughout the rest of the continuous production process, resulting in a long sheet.

[0086] If the sheet is cut into ribbons, or the production method employs substrate wires or ridged substrate surfaces as described above, the ends of the resulting graphene ribbons may be grasped and pulled off. The continuous production process continues as the layer of substrate 8 on the rotating drum 6 or tube 38 continues to rotate back into the reaction chamber 4, and the now bare/uncoated substrate layer will again be coated with graphene deposits.

[0087] In the case of cut ribbons of graphene, or separate graphene ribbons formed by use of the wire substrates, the resulting plurality of free graphene ribbons may be twisted into long, continuous strands of graphene yarn. As the yam is twisted, the graphene ribbons will collapse, eliminating the free space between individual ribbons. The graphene yarn may be pulled (tensioned) sufficiently that a dense fiber is obtained. The graphene yam may then be bundled into a fiber tow for later use in industrial or commercial applications, such as use in carbon fiber cloth weaving, or use for fiber winding around high pressure gas storage vessels. The graphene ribbons do not have to be twisted into yarn, but could be maintained generally parallel to each other and then tensioned.

[0088] In an embodiment, a correction process may be conducted on the graphene in a correction apparatus 56 provided in a correction zone of the apparatus. The correction process may be conducted after removal of the graphene 14 from the catalyst substrate 8, in order to correct defects in the graphene structures such as holes or carbon vacancies. After the graphene sheets or ribbons 14 have been removed from the drum 6 or tube 38, the graphene 14 may be passed through a correction zone. The correction zone may comprise correction apparatus 56 which may include a secondary reaction chamber where heat is provided up to 1500°C and a hydrocarbon source is provided. In this secondary reaction chamber, the hydrocarbon will be decatenated, allowing pure carbon to deposit on the graphene at the points of the defects. In an embodiment, the correction process may be accomplished or aided by a correction apparatus 56 that conducts a process to introduce pure carbon vapor to the graphene 14 to promote self-healing, whereby the carbon in the vapor is attracted by the graphene 14 and bonds with the graphene 14 to fill in the areas of defects. This carbon vapor process takes advantage of the self-healing properties of graphene. Correcting defects in graphene products is important for maintaining high optical, electrical, and mechanical properties in the resulting products.

[0089] A method is claimed of graphene production comprising steps as described above in more detail in connection with the apparatus. It may be appreciated from the description above that method steps may include producing graphene using a decatenation reaction whereby carbon is released from a carbon source such as a hydrocarbon precursor through application of heat to the carbon source in the presence of a catalyst. The method may include providing a substrate disposed on a surface of a cylindrical body, and rotating the cylindrical body so that the substrate is passed through a reaction zone such as a reaction chamber containing the carbon source. Heat is provided to drive the decatenation reaction, causing carbon to deposit as graphene on the substrate on the cylindrical body as it rotates around its central longitudinal axis. The heat is applied at a graphene production temperature sufficient to drive the decatenation reaction.

[0090] In the method, the produced graphene is released from the substrate. The release maybe aided by cooling of the substrate on the side of the rotating body that is no longer inside the reaction zone of the apparatus, namely a cooling zone, such as by employing a cooling apparatus disposed outside the reaction zone. The cooling may be accomplished by internal cooling from an inner side of the rotating body, or external cooling of the rotating body. Graphene may be released by use of a laser to score or cut the graphene to aid release, and/or to provide the graphene product in a desired form, such as a ribbon form. The correction process as previously described above may then be used to correct any defects in the graphene product.

[0091] The method and apparatus disclosed herein yield improved graphene ribbon and sheet products that may be many meters in width and infinite in length, in a continuous production process. The invention provides improvements in the ability to select and control particular hydrocarbon precursors, substrates, and reaction conditions to yield graphene products having particular desired formats and physical and chemical characteristics, in an energy-efficient and cost-effective production process.

[0092] The process and apparatus are easily adapted for continuous graphene production, while employing just one major moving component (the drum 6 or rotating tube 38). This process and apparatus thus enjoy low wear and tear and replacement costs, especially as compared to prior art systems and methods employing many moving parts. One of the critical features of the claimed invention is simplicity in design and low cost in making, using, and repairing the apparatus and practicing the claimed method. By reason of this simplicity, the overall operating expenses and capital expenditures of the system and method are greatly reduced compared to previous devices and methods. For this reason, the inventors consider to be fully within the scope of this invention those eembodiments that lack, and/or those embodiments that explicitly exclude, certain features that may be described herein or in the prior art, such as additional moving components.

[0093] It is to be understood that the above description is intended to be illustrative, and not restrictive and while the invention has been has been described herein in detail, only exemplary embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention are considered to be within the scope of the invention to be protected. The drawings are merely schematic representative, and should not be interpreted as being to scale or accurately represe ting relative distances between or relative size of respective components. Many other embodiments will be apparent to those of skill in the art upon reading and understanding the above description. For example, it is contemplated that features described in association with one embodiment are optionally employed in addition or as an alternative to features described in association with another embodiment.

[0094] It should be understood that while the use of words such as "preferable" or preferably" used herein may indicate that the feature is desirable, the feature nonetheless may not be necessary to the claimed invention. In reading the disclosure and claims, it is generally intended that when singular terms such as "a,' " "an," " 'at least one,' " and the like are used, there is no intention to limit to only one item unless specifically stated to the contrary. ' The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

REFERENCE NUMERAL LISTING

2 apparatus

4 reaction chamber

6 rotating drum

8 catalyst substrate

10 axle

12 laser

14 graphene product

16 liquid HC reservoir

i 8 chamber outlet for H 2 gas

20 ridge formed in drum

22 fin on drum

24 central portion of drum

26 drive motor system

28 drum core

30 ceramic outer layer of drum

32 segment of ceramic outer layer of drum

34 gap between ceramic layer segments

36 interior heating apparatus of drum

38 hollow rotating tube

40 stationary core

42 gap between tube and core

44 internal heating apparatus of stationary core

46 internal cooling apparatus of stationary core

48 heat exchanger in stationary core

50 chamber inlet for hydrocarbon gas

52 external heat source

54 cooling gas channel correction apparatus carbon source (hydrocarbon hydrogen gas

cooling gas

longitudinal axis of drum